System and method for calibrating force sensors

Abstract

A system, method, and computer program product for calibrating force sensors is provided. The force sensors can be provided in a wearable device worn by a user underfoot. A force sensing apparatus has a plurality of apparatus force sensors and a charging unit. The charging unit can charge an energy storage device of the wearable device when the wearable device is received on the upper surface of the apparatus. The force sensing apparatus can sense a force applied to the upper surface of the apparatus when the wearable device is worn by a user while standing on the upper surface of the apparatus. At the same time, the force sensors in the wearable device can generate sensor readings. The system can determine a calibration model for the device force sensors by comparing the force values from the apparatus force sensors and the device force sensors in the wearable device.

We claim: 
     
         1 . A system for calibrating a plurality of force sensors in a wearable device worn by a user, wherein the plurality of force sensors are positioned underfoot, the system comprising:
 a force sensing apparatus comprising an upper surface and a plurality of apparatus force sensors, wherein the upper surface is configured to receive the wearable device while the wearable device is worn by the user, the plurality of apparatus force sensors are arranged below the upper surface, and the plurality of apparatus force sensors are configured to sense a force applied to the upper surface;   a charging unit operable to charge an energy storage device of the wearable device when the wearable device is received on the upper surface;   one or more processors in communication with the wearable device; and   a non-transitory storage memory;   wherein the one or more processors are configured to
 determine a first measured force value, wherein the first measured force value is determined based on a first plurality of measured sensor readings from the plurality of force sensors while the wearable device is worn by the user while standing on the upper surface; 
 determine a second measured force value, wherein the second measured force value is determined based on a second plurality of measured sensor readings from the plurality of apparatus force sensors while the wearable device is worn by the user while standing on the upper surface; and 
 determine a calibration model for the plurality of force sensors by comparing the first measured force value and the second measured force value. 
   
     
     
         2 . The system of  claim 1 , wherein the force sensing apparatus further comprises an apparatus inertial measurement unit (IMU) and the one or more processors are configured to:
 obtain concurrent first IMU angle measurement and second IMU angle measurement, wherein the first IMU angle measurement is obtained from a wearable device IMU provided by the wearable device while the wearable device is worn by the user while standing on the upper surface and the second IMU angle measurement is obtained from the apparatus IMU;   determine a device IMU angle for the wearable device IMU by comparing the first IMU angle measurement and the second IMU angle measurement; and   output the device IMU angle.   
     
     
         3 . The system of  claim 1 , wherein the one or more processors are configured to store the calibration model in the non-transitory storage memory, wherein the non-transitory storage memory is contained within the wearable device. 
     
     
         4 . The system of  claim 1 , wherein the wearable device is an insole. 
     
     
         5 . The system of  claim 1 , wherein the force sensing apparatus is portable and foldable. 
     
     
         6 . The system of  claim 1 , wherein the force sensing apparatus further comprises a receptacle within which the wearable device is receivable when the wearable device is not being worn by the user. 
     
     
         7 . The system of  claim 1 , wherein the charging unit is operable to charge the energy storage device, and the plurality of apparatus force sensors are concurrently operable to sense the force applied to the upper surface when the wearable device is received on the upper surface. 
     
     
         8 . The system of  claim 1 , wherein the charging unit is a wireless charging unit. 
     
     
         9 . The system of  claim 1 , wherein the charging unit is operable to charge the wearable device over a defined portion of the upper surface and the upper surface includes an alignment guide indicating the defined portion of the upper surface upon which the wearable device is receivable to undergo charging by the charging unit. 
     
     
         10 . The system of  claim 1 , further comprising a housing containing the plurality of apparatus force sensors and the charging unit, the housing defining the upper surface. 
     
     
         11 . The system of  claim 10 , wherein the force sensing apparatus comprises an electronics module associated with the plurality of apparatus force sensors, the charging unit comprises a transmitter coil, and the housing further comprises shielding arranged to shield the transmitter coil from the electronics module. 
     
     
         12 . A method of calibrating a plurality of force sensors in a wearable device worn by a user, wherein the plurality of force sensors are positioned underfoot, the method comprising:
 determining a first measured force value, wherein the first measured force value is determined based on a first plurality of measured sensor readings from the plurality of force sensors while the wearable device is worn by the user while standing on an upper surface of a force sensing apparatus, wherein the force sensing apparatus comprises a plurality of apparatus force sensors arranged below the upper surface and the plurality of apparatus force sensors are configured to sense a force applied to the upper surface;   determining a second measured force value, wherein the second measured force value is determined based on a second plurality of measured sensor readings from a plurality of apparatus force sensors while the wearable device is worn by the user while standing on the upper surface; and   determining a calibration model for the plurality of force sensors by comparing the first measured force value and the second measured force value.   
     
     
         13 . The method of  claim 12 , wherein the force sensing apparatus further comprises an apparatus inertial measurement unit (IMU) and the one or more processors are configured to:
 obtain a first IMU angle measurement from a wearable device IMU provided by the wearable device while the wearable device is worn by the user while standing on the upper surface;   obtain a second IMU angle measurement from an apparatus IMU of the force sensing apparatus, wherein the first IMU angle measurement and the second IMU angle measurement are concurrent;   determine a device IMU angle for the wearable device IMU by comparing the first IMU angle measurement and the second IMU angle measurement; and   output the device IMU angle.   
     
     
         14 . The method of  claim 12 , wherein the force sensing apparatus is portable and foldable. 
     
     
         15 . The method of  claim 12 , further comprising charging an energy storage device of the wearable device when the wearable device is received on the upper surface. 
     
     
         16 . The method of  claim 15 , wherein the energy storage device is charged concurrently while the first plurality of measured sensor readings are obtained. 
     
     
         17 . The method of  claim 15 , wherein the energy storage device is charged at a time other than when the first plurality of measured sensor readings are obtained. 
     
     
         18 . The method of  claim 15 , wherein the energy storage device is charged wirelessly. 
     
     
         19 . The method of  claim 15 , further comprising aligning the wearable device with a defined portion of the upper surface using an alignment guide, wherein the defined portion is a region of the upper surface upon which the wearable device is receivable to undergo charging. 
     
     
         20 . The method of  claim 15 , further comprising outputting a visual indicator while the wearable device is undergoing charging.